Apparatus for telephoning.



I No. 887,533 PATENTED MAY 12, 1908.

F. SINDINGCHRISTENSEN. APPARATUS FOR TELEPHONING.

APPLIOATION FILED MAY 17 1001.

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,7 F I ERIE]- .INVENTUR H15 ATTUR gfiV \A ITNESEES A Q No. 887,538.PATENTED MAY 12, 1908. F. SINDINGGHRISTENSEN.

APPARATUS FOR TELEPHONING.

APPLICATION FILED MAY 17, 1901.

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FREDERIK SINDINGCHRISTENSEN, OF NEW YORK, N. Y., ASSIGNOR TO WILLIAM H.LOCKE,

.llt, OF BROOKLYN, NEW YORK.

APPARATUS FOR TELEPHONING.

Specification of Letters Patent.

Patented May'12, 1908.

the telephone to carry farther than has heretofore been foundpracticable, as well as to increase its efiectiveness for shorter lines,more particularly such as have heretofore overtaxed the capacity of thetelephone.

By my invention not only is interference, from'other circuits minimizedor practically obviated, but the electrical capacity of the line,instead of looming u as an obstacle, as heretofore, is turned to avantage, so that a line of great capacity may transmit better than a hneof very small ca acity. The line wire may hence be of consi erablethickness, if desired.

In telephoning, one end of an induction coil is joined or electricallyconnected to the transmitting line-conductor, and the other end of saidcoil is grounded. A receiver is connected to the far endof the otherlineconductor, that is to say, the coil usually forming part of thereceiver is so connect while. thefother end of said receiver coil isgrounded. Thusa broken circuit is formed, beginning say at'the dead endof the receiv ing line-conductor, and extending thence to the receivingstation, thence through the earth back to the transmitting station, andthence to the dead end of the transmitting line-conductor. J Thesound-generated or produced electricity present in the induction coilflows or spreads through the transmitting line-conductor toward the farstation,

and throughout its flow induces correlative or opposite-signelectrification of thereceiving line-conductor, so that the appliancesconnected to the far end of the latter are affected accordingly, causingthe reproduction of the original sound. p

In the accompanying drawings, Figure 1 is a diagram indicative of thegeneral arrangement of the form of telephonic apparatus preferred for aprivate line, including transmltters, receivers, and a main line (thelatter consisting of parallel conductors) extending between stations.lnorder to indicate great length, theline is represented in this figureas extending in a zigzag direction. Fig. 2 is a diagram illustrative ofa method of si naling from either station-to the other. .3 is a diagramof a portion of a main line, illustrating a method of crossing ortwisting exposed overland line-conductors, so as to reduce interferencefrom other lines or from earth currents. Fig. 4 is a cross section of aland cable containing inductively cooperating conductors separated by adielectric. Fig. 5 is a plan, upon an enlarged scale, of the apparatusemployed at each end of the main hne at Fig.-2, for both making a visualsignal to the receiving operator, and also closing a local bell circuitat the receiving end of the line, thereby giving in addition an audiblesi nal. V Fig. 6 is a diagram illustrating a telep one trunk line withits branches. Fig. 7represents, upon an enlarged scale, a cross-sectionof a land cable taken through a condenser, and giving an edge view ofthe condenser armatures and a dielectric. sheet, spread open. Fig. 8 isa side view of the devices illustrated at Fig. 7, and shows how thecable may at intervals be stripped of its insulation, thus laying theconductors bare, so that condensers may be applied thereto.

Fig. 9 is a dia ram illustrative of a broken induction circuit, of whichthe earth forms the return member. Fig. .10 is a diagram of a simplifiedtelephonic apparatus.

In the several-views, similar parts are designated by similar numeralsof reference.

At Fig. 1 the terminal apparatus is sub- I stantiallyduplicated at thestations, so that conversation may be conducted over the line. 1. desinates a primary coil and 2 a battery, both included in a transmittercircuit 3, a transmitter of the usual type'being depicted at 4. At5 isrepresented an induction coil, one end whereof is grounded at E, and theother end whereof is connected, (through the usual coil of a telephonereceiver 6) to a line conductor. Twin line-conductors are indicated, onethereof, marked 7, being connected at one end to the induction coil 5 atthe left. of said figure, and being insulated orit necessary,the'condensers may he applied ,more readily induce electrification ofthe and since the latter may be Wound with finer duction coil 5 may bemade sharper, and of mutual capacity of the line-conductors them- Widelyse arated and can directly afiect each end to the induction coil 5 atthe right of said figure, and is also insulated at its inactive terminal8*.

As the efiectiveness' of the apparatus depends in a large measure uponthe mutual electrical capacity or upon the degree of the mutualinductive action of the line-conduct-. ors, I recommend that suchcapacity or inductive power be augmented by means of a number ofcondensers 9, joined in parallel by v the line-conductors and arrangedat intervals of one to ten miles or more, the frequency of thecondensers depending upon their individual capacities, the proximity andhence the selves, the liability of interference from other circuits orfrom earth currents, etc. Where the line is short, or Where other causesmake at less than mile intervals, in order to secure the requiredcapacity. i /hen the line-con ductors run closely side by side, one mayother, and hence there is less need for the ap plication of condensersat frequent intervals, and in some'oases the condensers may even beomitted; but where the conductors are other litt eor perhaps not at;all, it becomes necessary to provide them with one or more condensersbetweenstations, in order to enable the line-conductors to cooperate.

W hen sound enters the transmitter, say at the left of Fig. 1,undulations are set up in the transmitter circuit 3, as usual in telephony or in other words, rapid fluctuations occur in the quantity ofelectricity flowing in the circuit, and by an inductive process the coil5 is affected accordingly. A sudden in crease in the strength or voltagein the primary current and hence in the flow of electricity through theprimary coil 1 induces a negative electrification of the induction coil5, While a sudden decrease in the primary current induces a positiveelectrification of the induction coil. Such changes follow on anotherWith great rapidity in the primary coil and in the surrounding inductioncoil,

wire and may have more turns than the former the fluctuations roduced inthe inmore Widely varying potential.

For convenience, tne mutating electrical conditions of the coil 5 may beregarded as electrostatic, or as charges rather than cur rents. When anegative charge is induced in said coil 5 by the primary coil, apositive charge is repelled toearth at E, While said negative charge isdistributed both along the condenser armatures which are joined to saidconductor, thereby inducing a positive charge both in the otherline-conductor 8 and in the condenser armatures which are joined to thelatter, and hence repelling a negative senses charge to earth throughthe coil mounted in the receiver 6 joined to the receiving lineconductor 8 at the station upon the r1ght of Fig. 1, whereby the barmagnet in said receiver is affected, and causes the diaphragm usuallyarranged therein to generate or" rather reproduce sound.

It Will be understood that thegnegative charge repelled to earth throughthe receiver at the right-hand station substantially balances thepositive charge repelled to earthfrom the induction coil 5 at theleft-hand station, and hence that the earth serves as a return. The linecircuit may therefore be regarded as beginning at 8", and extendingthence along the conductor8 and throu h the receiver-coil joined theretointo cart thence back through the earth to the induction coil 5 at theleft-hand station, and thence along the line-conductor 7 to itstermination at 7, as illustrated at Figs. 1 and 9. By means of theground connection, the instruments at the respective stations areelectrically connected independently of the lineconductors Although theline circuit is broken, so that a continuous current may not flow aroundthe same, still it Will be understood that in a broad sense the circuit,forms a complete operative device, and that the mutual inductivity ofthe parallel lineconductors may be regarded as a substitute for theexpedient heretofore practiced of sending a current directly around aclosed circuit from one station to another and back to the startingpoint.

Thus it Will be perceived that the varying electrical impulsesoccasioned bythe entrance of sound. into the transmitter are caused toflow towards the receiving station, and to induce correlative impulsesin a line- 5 conductor which extends from the far station towards thetransmitting station, such induction preferably taking place throughoutthe entire flow orspread of the charges or impulses along thetransmitting line-conductor; or in other words, the electrification ofthe receiving line-conductor is effected at successive points throughoutthe flow of the transmitting charges towardsthe receiving station, thatis, said transmitting charges 5 perform their function en route. Thereceiving line-conductor may thus be directly affected by thetransmitting line-conductor right up to the receiving station, so thatthe distance over which either Wire 7 or 8 acts 12o merely as a solitaryline for the conveyance of electrical impulses may be reduced to nil.Hence in one view of the invention, the telephone line heretofore emloyed may be regarded as being eliminated, even though the stations maybe separated by many leagues; and the earth-connected line-conductors,taken together, may be regarded simply as constituting an instrumentextending from one station to the other, its internal operasenses tionsbeing performed with practically uniformpower and effectivenessthroughout its length, and the impulses delivered at one end thereofcomparing quite favorably in point of strength and sharpness with theimpulses sent into the other end thereof. In this connection it will beperceived that by correlating the conductors 7 and 8, so that themomentary charges in each may be bound by the charges in the other,interference from other circuits or from earth currents may bepractically eliminated. The more intimately the conductors areassociated, or the reater their mutual capacity, the less will theirwork suffer by reason of outside interference. Moreover, the solitaryline over which the impulses must ass before the correlative actionbegins or a ter it ends may be eliminated, or at least so shortened asnot to impair the efficiency of the apparatus.

Inthe foregoing description it has been assumed that sound is originatedat the lefthand station at Fig. 1 and emitted or reproduced at theright-hand station; but it will be observed that the appliances at eachstation .are substantially duplicate, so that sound spoken into thetransmitter at the right-hand station may be reproduced at the left-handstation. In this. case the wire 8,- which is joined to the secondary 5of the transmitting apparatus at the right-hand station, acts as thetransmitting line-com ductor, and induces impulses in the wire 7 whichin this case acts as receiving line-conductor, whence the impulses flowthrough the coil in the receiver 6 at the left-hand station' and intoearth. Thus it will be seen that the impulses generated at eitherstation .joined in para lel by the line-conductors so as to increase thetotal capacity of the line. One advantage of large capacity in my systemarises from the increased or more power ful charge of electricity thatis caused to flow from the secondary coil into the lineconductor, sothat a greater amount of electricity is repelled oppositely from saidcoil to'earth; a'nd correlatively a greater charge is induced in thereceiving line-conductor and a greater amount of electricity is re-..pelled to earth through its receiver coil,

which correspondingly affects the receiver diaphragm, so that the latteris more powerfully actuated.

Although by the enlargement of the area i or capacity of thetransmitting conductor the potential thereof at all oints iscorrespondingl reduced, nevert eless the extension 0 the inductionsurface secured by introducing the condensers enables a larger aggregatecharge to be induced in the receiving line-conductor, and the inductiveaction is hastened, so that the receiver diaphragm is given a quick andpowerful vibration. A further advantage'of enlarged capacity resides inthe fact that the opposite electrifications' simultaneously permeatingthe line are more closely bound together, and hence less liable to' beaffected by the earth return or by any outside influences. The morefrequent andca acious the condensers 9, the less the liabi ity ofinterference, and the more faithfull are the original impulsesreproduced at t e receiving station; and it is obvious that by employingsuitable frequency and capacity of condensers, interference may bepractically eliminated.

Each of the conductors may consist of either a single coarse Wire or ofa strand of wires, orany other form of conductor may be em loyed. Byplacin the conductors close a ongside of each ot er, their mutualcapacity is increased, with corresponding benefit, although they-shouldnot be placed so closely together that disruptive discharges will beliable to occur between them. By making the conductors of suitable sizeand length, and associating them closely together, somuch capacity maybe secured, that the condensers may be omitted.

In an overland. cable (Fig. 4), the twin conductors may be made of thickwire and lie closely side by side, forming a double core, each conductorbeing embedded in a sheath 10 of rubber or other dielectric, the latterbeing provided with one or more fibrous or other coverings 11.

It. is not essential that the terminal apparatus should be arrangedprecisely as indicated at Fig. 1, or operate in precisely the mannerdescribe The invention is notlimited to the methods of electrifying thetransmitting line-conductor detailed herein. 'In adapting the generalfeatures of invention to other specific uses, other means may of coursebe employed for electrifying one of the conductors com prised in theline, and the electrification induced in the other of said conductors,or dis-- charging into return' therefrom, may be utilized by otherterminal appliances.

At Figs. 2 and 5 is illustrated a form of electroscope which may beemployed in calling or sending signals of any sort from one station tothe other. A set of fixed quadrants 15 is connected at each station tothe insulated end (7 or 8) of the receiving line-conductor. Just overthe quadrantsa flat light needle 16 is suspended by means of a thintorsion wire 17, and the transmitting line conductor .is connectedthereto. Switches .18- may be interposed between the electroscope andthe line-conductors, whereby the former may be cut out when thetelephone is in active use. When the switches are closed, charges ofopposite sign present in the lineconductors may flow or distribute intothe quadrants and needle respectivel ,and in consequence the vanes ofthe nee le will be attracted by the uadrants, and hence rotate fromtheir norma positions above the gaps,

and take positions directly over the.'quad.

rants, the suspending wire 17 being of course the axis of rotation. Thequadrants maybe made of brass or copper, and the needle may consist offoil spread upon the under side of a suitably shaped card. At eachstation is provided a battery 19, which the operator the far end of theline is electrified, and

whereby also a charge of opposite sign is induced in the receivingline-conductor (from whose remote end an equal charge is repelled toearth), so that the far needle 16 becomes likewise charged and is causedto vibrate, thus visually notifying the far operator that his station isbeing called.

An audible signal may be produced by rigidly mounting an aluminium orother circuit-closer 21 upon the needle, whereby a local bell-circuit 22may be completed, causing a bell to ring at-B, thus indicating to boththe eye and ear of the operator that the other operator is calling. Ofcourse neither lineconductor should be so powerfully electrified as tocause a disruptive discharge to occur at any point, particularly in thecondensers, when these are employed. Other methods of signaling may beresorted to.

Instead of grounding the telephone coils to which the active ends of theline-conductors are joined, said coils may be connected by a return wire23, as indicated by a dotted line at Fig. 2, which may be ofconsiderable thickness, and should be as widely separated.

as practicable from the line-conductors 7 and 8 included in the samebroken circuit therewith, so as to avoid disturbance of the charges insaid conductors, which might otherwise occur because of the mutualattraction between the return and the conductors.

At Fig. 3 is illustrated a method of crossing exposed lineconductors atintervals, whereby liability of interference either from other currentsor from return may be reduced. 1

At Fig; 6 line-conductors are indicated as extending in pairs betweencentral stations ceases or tele hone exchanges, the latter =be' markedat A, D, F, G, H, J, L, M, and R.

a subscriber S, connected say to central office G, desires to conversewith a subscriber whose lines run to any other central oflice, as

at J, one of the usual twin local lines goingv from G to S is groundedat G, and the other thereof is connected with the line-conductor 7 andat each of the intervening central stations A, D, R, and H appropriateconnections are made, so that the line-conductors 7 and 8 may extendunbrokenly from G to J.

length, so that by the use of a few trunk' lines and ramifying locallines, telephoning may be conducted among points distributed over wideterritory, any subscriber being able to converse with any othersubscriber throughout the system.

What I claim as new, and desire to secure by Letters Patent, is asfollows:-

1. A telephonic apparatus comprising lineconductors, condensersarrangedat intervals therealong and joined in parallel thereby, a groundedinduction coil joined to one end of one of said line-conductors, atransmitter circuit for aflecting said induction coil, and a groundedreceiver connected to theremote end of the other line-conductor.

2. A telephonic apparatus comprising lineconductors, condensers arrangedat intervals therealong and joined in parallel thereby, an inductioncoil joined to one end of one of said line-conductors and forming partof a transmittin appliance, a receiver joined to said coil, a ikeinduction coil and a receiver both joined to'the remote end of the-otherlineconductor, and means for electrically connecting said inductioncoils and receivers independently of said line-conductors.

3. A telephonic apparatus comprising lineconductors running closely sideby side, each having one end free, condensers arranged at intervalstherealong and joined in parallel thereby, grounded transmitting andreceiving devices connected to one end of one of said line-conductors,and grounded transmitting and receiving devices connected to the remoteend of the other of said line-conductors.

4, A telephonic apparatus comprising a transmitter circuit including aprimary coil, a grounded induction coil joined to one end of aline-conductor, a grounded receiver also connected to said end of saidline-conductor; a second line-conductor, condensers arranged atintervals along said line-conductors and remote end of theotherline-conductor for rendering intelligiblev impulses induced thereinby the transmitting line-conductor, and means forelectrically connectingsaid sending means with said receiving means independently of saidlineconduetors.

Signed at Elizabeth, State of New Jersey, 20 this 15th day of May,190-1.

FREDERIK SINDINGCH RISTENSEN.

Witnesses:

B, (3. Summer, 7 BENJAMIN M. OGDEN.

joined in parallel thereby, a grounded induetion coil joined. to theremote and of said second line-conductor, a transmitter circuitincluding a primary coil for effecting the last mentioned inductioncoil, and a grounded receiver also joined to said remote end of saidsecond line-conductor.

5. An apparatus for the transmission of intelligence, comprisingline-conductors, condensers arranged at intervals therealong and joinedin parallel thereby, means for send- 1 ing Varying impulses into one endof one ol' 1 said line-conductors, means connected to the i

